Pouring semi-flexible pavement (SFP) material is a multi-phase composite with excellent pavement performance, which consists of porous asphalt mixture (PAM) and grouting material. This research is to investigate the optimal design of SFP for the upper pavement layer in relation to air void and thickness. Firstly, the effect of PAM with different air voids on the mechanical performance of SFP is investigated by uniaxial compression tests. Secondly, the influence of the air void of PAM on the rutting resistance and water sensitivity of SFP is analyzed by wheel tracking test and Hamburg wheel tracking (HWT) test. Then, the optimal thickness of SFP is investigated by 3D finite element analysis. Finally, based on the experimental and numerical results, SFP is applied to practical engineering and the field performance was inspected. The results show that increasing the air void of PAM can significantly improve the mechanical properties and rutting resistance of SFP. However, when the air void of PAM is 25%, SFP has the highest strain energy density. According to the experimental and numerical results, as well as the construction cost of SFP, the optimal thickness range of 4-8 cm is recommended for the SFP layer. Moreover, the field performance inspection results show that after nearly 2 years of service, pavement using SFP with PAM air void of 25% and thickness of 4 cm for the upper layer has excellent rutting resistance, impermeability, and high wear resistance, which allows for undergoing heavy traffic loads.
